The paper deals with the design optimization of a voltage source inverter (VSI) fed squirrel cage induction motor. A set of nine independent variables is selected and to make the machine feasible and practically acceptable certain constraints are imposed on the design. Different objective functions are considered, namely, the active material cost, operating cost, a mixed objective function of the active material cost and operating cost, and the torque pulsation, to facilitate a suitable design for a given application. In this investigation the sequential unconstrained minimization technique (SUMT) with interior penalty function approach in conjunction with Rosenbrock's method of rotating coordinates is used to optimize the design. The optimized design results of a 7.5 kW, delta-connected, voltage source inverter fed cage motor are given and discussed in detail.